Deirdre Budd’s Blog

Diabetes and Circadian Rhythm

Posted on: June 21, 2010

The body’s primary circadian clock resides deep in the brain, but local biological clocks also are found in tissues throughout the body, including the pancreas, lungs, liver, heart and skeletal muscles. These clocks operate on a 24-hour, circadian (Latin for “about a day”) cycle that governs functions such as sleeping and waking, rest and activity, fluid balance, body temperature, cardiac output, oxygen consumption, metabolism and endocrine gland secretion.

As part of this system, our fundamental body systems such as sleep wake cycles and when we feel hunger are also regulated. Recent research, led by Bass and Biliana Marcheva,  first author of the paper, involving key collaborators Louis H. Philipson of the University of Chicago, Joseph S. Takahashi of the University of Texas Southwestern Medical Center and Seth D. Crosby of the Washington University School of Medicine. Looked at the development of diabetes and the links between insulin production and the circadian rhythm.

In their study, the researchers knocked out the clock genes in islet beta-cells in mice, and found the animals developed impaired glucose tolerance, and abnormally low levels of insulin. They went on to develop diabetes. The clock of the beta-cell coordinates glucose management, and the loss of the clock inhibited the cells from secreting insulin.

These findings will help in working out the causes of glucose abnormalities, but there is still a lot to learn. The researchers showed that insulin-secreting islet cells in the pancreas, called beta-cells, have their own dedicated clock. The clock governs the rhythmic behavior of proteins and genes involved in insulin secretion, with oscillations over a 24-hour cycle. “This is the first evidence of how the circadian clock may affect the development of diabetes,” said Joe Bass, M.D. “The biological programs in animals for harvesting energy, are under control of this clock.”

 “The variation we see in insulin secretion in humans, and susceptibility to diabetes, is likely related to this clock mechanism,” said Bass, an endocrinologist trained in molecular genetics. “There is an association in the changes of the cycling of the clock within the pancreas itself and disease. The question is, can we can modulate this?”

Diabetes is the seventh most common cause of death in America and costs every country a huge amount in health care and disablilty. Anything which can reduce the impact or the number of people who suffer from the effects of diabetes should be welcomed.


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June 2010
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